Emissão de gases de efeito estufa e mitigação de N2O na produção de bovinos de corte em pastagens tropicais

Author(s)

Abmael da Silva Cardoso

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2016-03-02.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2016-02-03
• Advisor: Ana Cláudia Ruggieri

Abstract

CH4 and N2O are two of the most important greenhouse gas emitted by livestock. They are produced from animal excretes and the fertilizer. In Brazil the amount and options to mitigate these gases are little explored. We carried out a sequence of 4 field-trials (two rainy and two dry season, 106 days each) aimed to quantify the N2O and CH4 emissions, NH3 volatilization and emission factor (EF) after application of dung, urine, dung + urine and urea fertilizer on a Ferralsol of a marandu palisade-grass pastureland of Brazil. We aimed to investigate the effects of soil moisture, soil compaction, urine composition, urine volume, and dung addition on N2O emission from a urine-treated tropical Ferralsol under controlled conditions as well on CH4 emission. As option to mitigate greenhouse gas (GHG) emissions we studied how grazing heights affect the magnitude of GHG emissions; how season influence GHG production and consumption; what are the key driving variables associated with GHG emissions. Additionally, we investigated the effect of dietary mineral salt levels on urine-N concentration, urine volume, the proportion of N compounds in the urine and faeces-N concentration under field conditions. The emissions factor (EF) calculated differed according excretes and season. The EFs were 2.34%, 4.26% and 3.95% in the rainy season and 3.00%, 1.35% and 1.59% in the dry season, respectively, for the dung patches, urine patches and dung + urine. The N2O EF from urea was 0.37%. The averages of CH4 accumulated emissions were 99.72, 7.82 and 28.64 (mg CH4-C m2) for dung, urine and dung + urine in this sequence. The manipulated soil conditions moisture content, compaction, and dung addition affected N2O emissions when varying quantities of urine-N were applied (in equal urine volumes) being higher when added dung and did not affect when varying urine volumes were applied (containing equal quantities of urine-N). The urine-N concentration influenced N2O emissions decreasing from the lower concentration to the higher and the chemical form of urine-N did not. The concentration of KCl added to the urine influenced N2O emissions presenting a curvilinear curve. When the CH4 emissions were influenced by soil factors moisture content, compaction and dung addition and did not responded to the variation in the urine-N concentration and volume. The source of N did not influence the CH4 emissions/oxidation. Pasture height, season and year affect N2O and CO2 emissions and the season CH4 releases. The greater emissions occurred in the summer and the lower in the winter. Pasture height had negative linear effect on annual cumulative N2O emissions and positive linear effect on annual cumulative CO2 emissions. Dietary effects of mineral salt level influenced the N concentration in the urine, urine volume, urea-N, allantoin-N and hyppuric acid. While the total N excreted daily via urine, creatinine-N and N concentration in feces were not affected by mineral salt level in the diet. The emissions of CH4, N2O and NH3 differs that default EFs preconized by the IPCC. Soil moisture and compaction appear to be the main factors regulating N2O and CH4 emissions and depends of the rainfall seasonality. (AU)

• FAPESP's process: 12/06718-8 - Nitrogen balance, emission of greenhouse gases and mitigation of N2O in the production of beef cattle grazing.
• Grantee: Abmael da Silva Cardoso
• Support Opportunities: Scholarships in Brazil - Doctorate